Preconditioning for bitumen displacement

ABSTRACT

Methods and systems produce petroleum products with multiple horizontal wells through which injection processes precondition and displace the hydrocarbons in a formation. The wells extend through the formation spaced apart from one another in a lateral direction. Before fluid communication is established between the wells, cyclic injections and production of resulting backflow initiates conditioning of immobile products. Alternating between injection and production at adjacent wells may then facilitate establishing the fluid communication. After the fluid communication is established, a displacement procedure sweeps the hydrocarbons from one of the wells used for injection toward an adjacent one of the wells used for production.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims benefit under 35 USC §119(e) to U.S. Provisional Application Ser. No. 61/683,373 filed Aug. 15, 2012, entitled “PRECONDITIONING FOR BITUMEN DISPLACEMENT,” which is incorporated herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

FIELD OF THE INVENTION

Embodiments of the invention relate to producing hydrocarbons with multiple horizontal wells through which injection processes precondition and displace the hydrocarbons.

BACKGROUND OF THE INVENTION

Bitumen recovery from oil sands presents technical and economic challenges due to high viscosity of the bitumen at reservoir conditions. Steam assisted gravity drainage (SAGD) provides one process for producing the bitumen from a reservoir. During SAGD operations, steam introduced into the reservoir through a horizontal injector well transfers heat upon condensation and develops a steam chamber in the reservoir. The bitumen with reduced viscosity due to this heating drains together with steam condensate along a boundary of the steam chamber and is recovered via a producer well placed parallel and beneath the injector well.

However, costs associated with energy requirements for the SAGD operations limit economic returns and can make thin pay zones uneconomic to recover. Other past processes proposed to rely on cyclic injections but failed to recover enough of the bitumen for commercial success. Further, prior displacement methods utilized in reservoirs containing mobile hydrocarbons cannot enable recovery of the bitumen where immobile since the bitumen provides a barrier to flow between wells.

Therefore, a need exists for methods and systems for recovering hydrocarbons from oil sands including thin pay zones of immobile bitumen.

BRIEF SUMMARY OF THE DISCLOSURE

In one embodiment, a method of recovering hydrocarbons includes injecting during a first time a conditioning fluid through first and second wells and into a formation along lateral spaced apart and parallel horizontal lengths of the first and second wells. The method further includes producing the hydrocarbons recovered as backflow along the lengths of the first and second wells during a second time after the first time. Then, injecting the conditioning fluid into the formation along the length of the second well while producing the hydrocarbons along the length of the first well alternates with injecting the conditioning fluid into the formation along the length of the first well while producing the hydrocarbons along the length of the second well, thereby establishing fluid communication between the first and second wells. Next, injecting a displacement fluid into the formation along the length of the first well sweeps the hydrocarbons toward the second well and occurs while producing, along the length of the second well, the hydrocarbons being displaced.

For one embodiment, a method of recovering hydrocarbons includes injecting a conditioning fluid through first and second wells and into a formation at dispersed locations along parallel horizontal lengths of the first and second wells such that the injecting via the first well is offset in a lateral direction from the second well and aligned between the dispersed locations of the second well across from portions of the second well without fluid communication to the formation. Producing the hydrocarbons recovered as backflow at the dispersed locations along the first and second wells occurs after the injecting of the conditioning fluid. Then, injecting a displacement fluid into the formation via the dispersed locations along the first well sweeps the hydrocarbons toward the second well and occurs while producing, at the dispersed locations along the second well, the hydrocarbons being displaced.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and benefits thereof may be acquired by referring to the follow description taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic of three horizontal wells as viewed transverse to their horizontal length within a reservoir, according to one embodiment of the invention.

FIG. 2 is a schematic top view of the wells with dispersed flow control along their length and operated in an all injection cycle as depicted by arrows indicating fluid flow direction, according to one embodiment of the invention.

FIG. 3 is a schematic of the wells depicted in an all production cycle subsequent to the all injection cycle, according to one embodiment of the invention.

FIG. 4 is a schematic of the wells depicted in a first alternating injection and production cycle subsequent to the all injection and the all production cycles, according to one embodiment of the invention.

FIG. 5 is a schematic of the wells depicted in a second alternating injection and production cycle opposite and subsequent to the first alternating injection and production cycle, according to one embodiment of the invention.

FIG. 6 is a schematic of the wells depicted in a final displacement operation once fluid communication is established between the wells, according to one embodiment of the invention.

FIG. 7 is a schematic of the wells with resulting sweep of the reservoir by the final displacement operation shown by areas within dashed lines, according to one embodiment of the invention.

DETAILED DESCRIPTION

Turning now to the detailed description of the preferred arrangement or arrangements of the present invention, it should be understood that the inventive features and concepts may be manifested in other arrangements and that the scope of the invention is not limited to the embodiments described or illustrated. The scope of the invention is intended only to be limited by the scope of the claims that follow.

For some embodiments, methods and systems produce petroleum products with multiple horizontal wells through which injection processes precondition and displace the hydrocarbons in a formation. The wells extend through the formation spaced apart from one another in a lateral direction. Before fluid communication is established between the wells, cyclic injections and production of resulting backflow initiates conditioning of immobile products. Alternating between injection and production at adjacent wells may then facilitate establishing the fluid communication. After the fluid communication is established, a displacement procedure sweeps the hydrocarbons from one of the wells used for injection toward an adjacent one of the wells used for production.

FIG. 1 illustrates a formation 100 defining a hydrocarbon reservoir bounded between a bottom layer 101 and a top layer 102. While methods disclosed herein are applicable even if the formation 100 is greater than 15 meters, the formation 100 in some embodiments extends in height less than 15 meters, thereby limiting commercial applications of processes such as steam assisted gravity drainage. A first well 111, a second well 112 and a third well 113 each include horizontal lengths that pass through the formation 100.

As shown viewed transverse to the horizontal lengths, all the wells 111, 112, 113 in some embodiments align in a common horizontal plane or otherwise have the horizontal length in substantial horizontal alignment with one another. A lateral distance of between 5 and 50 meters may separate the wells 111, 112, 113 from one another. Costs of cycling depicted and described with respect to FIGS. 2 and 3 and accompanying revenue may influence duration of such cycling with longer durations enabling wider lateral separation, even greater than 50 meters, between the wells 111, 112, 113. The second well 112 extends between and is adjacent the first well 111 and the third well 113 without any additional intervening wells disposed between any of the wells 111, 112, 113. As visible in FIGS. 2-7, the horizontal lengths of the wells 111, 112, 113 may extend parallel to one another.

FIG. 2 shows the wells 111, 112, 113 operated in an all injection cycle as depicted by arrows indicating fluid flow direction. The all injection cycle may initiate while the wells 111, 112, 113 lack fluid communication with one another across the formation and may be an initial operation of the wells 111, 112, 113. The arrows in the all injection cycle indicate simultaneous injection of a conditioning fluid into the formation along the horizontal lengths of each of the wells 111, 112, 113.

For some embodiments, flow control devices 200 dispersed along the horizontal lengths of the wells 111, 112, 113 facilitate uniform or patterned injection and/or production along the horizontal lengths of the wells 111, 112, 113. The flow control devices 200 provide fluid communication from inside the wells 111, 112, 113 to the formation and can include orifices, perforations or slots in tubing or liner, well screen or other tortuous flow path assemblies. Valves or other metering devices may control inflow and/or outflow from the flow control devices 200.

Solid wall lined portions 201 of the horizontal lengths of the wells 111, 112, 113 may prevent fluid communication from inside the wells 111, 112, 113 to the formation. The lined portions 201 without fluid communication to the formation may separate the flow control devices 200 from one another along the horizontal lengths of the wells 111, 112, 113. In some embodiments, the flow control devices 200 of the first well 111 align between the flow control devices 200 of the second well 112 and across from the lined portions 201 of the second well 112. The flow control devices 200 of the third well 113 may also align across from the flow control devices 200 of the first well 111.

In some embodiments, the conditioning fluid as referred to herein and used in the all injection cycle can be any fluid capable of reducing viscosity or increasing mobility of the hydrocarbons by dissolving into the hydrocarbons and/or transferring heat to the hydrocarbons. The conditioning fluid may however not rely on any thermal application and may consist of only a solvent for the hydrocarbons. Economics may not support applying heat to the hydrocarbons with the conditioning fluid due to factors such thickness or extent of the formation.

For example, the solvent may be a lighter hydrocarbon than contained in the formation and may have 1 to 20 carbon atoms (C₁-C₂₀) or 1 to 4 carbon atoms (C₁-C₄) per molecule, or any mixture thereof. Examples of C₁ to C₄ hydrocarbon solvents include methane, ethane, propane and/or butane. The hydrocarbon solvent used as the conditioning fluid can be introduced into the formation as a gas or as a liquid regardless of its phase under reservoir conditions.

Composition of the conditioning fluid may also transition during any injection operation disclosed herein. For example, the all injection cycle may first utilize a liquid hydrocarbon solvent under reservoir conditions, such as diesel, for the conditioning fluid followed by a gaseous solvent under reservoir conditions, such as a mix of propane and carbon dioxide, for the conditioning fluid. Injecting the propane as a liquid may further provide drive energy upon flashing to gas in the formation to facilitate subsequent recovery.

FIG. 3 illustrates the wells 111, 112, 113 operated in an all production cycle during a subsequent time interval to the all injection cycle shown in FIG. 2. The arrows in the all production cycle indicate simultaneous recovery of the hydrocarbons along the horizontal lengths of each of the wells 111, 112, 113. Since the wells 111, 112, 113 still lack fluid communication with one another, the hydrocarbons can only backflow along with accompanying conditioning fluid to each of the wells 111, 112, 113.

The flow control devices 200 permit controlled inflow of the hydrocarbons into the wells 111, 112, 113 at where dispersed along the horizontal lengths of the wells 111, 112, 113. Processing the hydrocarbons produced to surface during the all production cycle may separate out the conditioning fluid for recycle. In some embodiments, cycling during additional time intervals between the all injection cycle shown in FIG. 2 and the all production cycle illustrated in FIG. 3 continues for multiple times and facilitates even distribution of the conditioning fluid injected into the formation.

FIG. 4 shows the wells 111, 112, 113 operated in a first alternating injection and production cycle subsequent to the all injection and the all production cycles. In the first alternating injection and production cycle, injecting the conditioning fluid through the second well 112 and out the flow control devices 200 along the horizontal length thereof occurs while producing the hydrocarbons recovered through the flow control devices of the first and third wells 111, 113. As evident, the third well 113 mirrors the first well 111 in function and arrangement and just provides a more complete picture of how further alternating well arrangements, i.e., the first well 111 and the second well 112, could continue to be disposed across the formation.

FIG. 5 illustrates the wells 111, 112, 113 operated in a second alternating injection and production cycle opposite and subsequent to the first alternating injection and production cycle. Specifically, injecting the conditioning fluid through the first and third wells 111, 113 and out the flow control devices 200 along the horizontal lengths thereof occurs while producing the hydrocarbons recovered through the flow control devices of the second well 112. For some embodiments, cycling during additional time intervals between the alternating injection and production cycles shown in FIGS. 4 and 5 continues for multiple times and facilitates establishing fluid communication between the wells 111, 112, 113.

FIG. 6 shows the wells 111, 112, 113 operated in a final displacement operation once fluid communication is established between the wells subsequent to operations illustrated in FIGS. 2-5. The arrows for the displacement operation indicate injection of a displacement fluid through the second well 112 and out the flow control devices 200 along the horizontal length thereof while producing the hydrocarbons recovered through the flow control devices of the first and third wells 111, 113. While the second well 112 for explanation purposes is selected for injection in the final displacement operation, direction of the arrows in FIG. 6 may match either FIG. 4 or FIG. 5.

Examples of the displacement fluid include gases or liquids capable of pushing the hydrocarbons through the formation. The displacement fluid may in some embodiments also facilitate recovery by further decreasing viscosity of the hydrocarbons in the formation. The displacement fluid may contain like constituents as the conditioning fluid described herein and which may likewise include any constituent described herein for use as the displacement fluid.

For some embodiments, the displacement fluid includes any combination of gaseous or liquid solvents for the hydrocarbons, water, steam, emulsifiers (e.g., surfactants, alkalis, polymers), air, oxygen and carbon dioxide. Heating any of the fluids used for the displacement fluid enables heat transfer to the hydrocarbons for viscosity reduction. Injection of combustibles, such as air or oxygen, as the displacement fluid enables starting in situ combustion during the displacement operation for recovery, which depends on the fluid communication being established between the wells 111, 112, 113.

FIG. 7 illustrates the wells 111, 112, 113 with resulting sweep of the formation by the displacement operation shown by areas within dashed lines. The displacement operation thus drives the hydrocarbons that are now mobile toward the first and third wells 111, 113 for recovery. The displacement operation recovers the hydrocarbons not produced during the operations shown in FIGS. 2-5 to gain desired cumulative recovery needed for commercial success.

In closing, it should be noted that the discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. At the same time, each and every claim below is hereby incorporated into this detailed description or specification as an additional embodiment of the present invention.

Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. It is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims, while the description, abstract and drawings are not to be used to limit the scope of the invention. The invention is specifically intended to be as broad as the claims below and their equivalents. 

1. A method of recovering hydrocarbons, comprising: injecting during a first time a conditioning fluid through first and second wells and into a formation along lateral spaced apart and parallel horizontal lengths of the first and second wells; producing the hydrocarbons recovered as backflow along the lengths of the first and second wells during a second time after the first time; then alternating between injecting the conditioning fluid into the formation along the length of the second well while producing the hydrocarbons along the length of the first well and injecting the conditioning fluid into the formation along the length of the first well while producing the hydrocarbons along the length of the second well, thereby establishing fluid communication between the first well and the second well; and then injecting a displacement fluid into the formation along the length of the first well to sweep the hydrocarbons toward the second well and while producing, along the length of the second well, the hydrocarbons being displaced.
 2. The method according to claim 1, further comprising cycling during additional time intervals between the injecting of the conditioning fluid and the producing of the hydrocarbons recovered as backflow.
 3. The method according to claim 1, wherein the conditioning fluid includes a solvent for the hydrocarbons.
 4. The method according to claim 1, wherein the conditioning fluid includes a solvent for the hydrocarbons that includes a liquid component under reservoir conditions and a gaseous component under reservoir conditions.
 5. The method according to claim 1, wherein the displacement fluid includes steam.
 6. The method according to claim 1, wherein the conditioning fluid includes a hydrocarbon solvent with between one and twenty carbon atoms per molecule and the displacement fluid contains steam.
 7. The method according to claim 1, wherein the displacement fluid includes at least one constituent selected from solvent for the hydrocarbons, water, steam, emulsifiers, air, oxygen and carbon dioxide.
 8. The method according to claim 1, wherein the conditioning fluid and the displacement fluid contain like constituents.
 9. The method according to claim 1, wherein the first and second wells are spaced between 5 meters and 50 meters apart in a common horizontal plane without intervening wells between the first and second wells.
 10. A method of recovering hydrocarbons, comprising: injecting a conditioning fluid through first and second wells and into a formation at dispersed locations along parallel horizontal lengths of the first and second wells such that the injecting via the first well is offset in a lateral direction from the second well and aligned between the dispersed locations of the second well across from portions of the second well without fluid communication to the formation; producing the hydrocarbons recovered as backflow at the dispersed locations along the first and second wells after the injecting of the conditioning fluid; and then injecting a displacement fluid into the formation via the dispersed locations along the first well to sweep the hydrocarbons toward the second well and while producing, at the dispersed locations along the second well, the hydrocarbons being displaced.
 11. The method according to claim 10, further comprising injecting the conditioning fluid into the formation via the dispersed locations along the second well while producing the hydrocarbons at the dispersed locations along the first well.
 12. The method according to claim 10, further comprising, following simultaneous injection through the first and second wells and simultaneous production through the first and second wells and until fluid communication is established between the first well and the second well, alternating between: injecting the conditioning fluid into the formation via the dispersed locations along the second well while producing the hydrocarbons at the dispersed locations along the first well; and injecting the conditioning fluid into the formation via the dispersed locations along the first well while producing the hydrocarbons at the dispersed locations along the second well.
 13. The method according to claim 10, further comprising cycling multiple times between the injecting of the conditioning fluid and the producing the hydrocarbons recovered at the dispersed locations along the first and second wells.
 14. The method according to claim 10, wherein the injecting of the conditioning fluid occurs simultaneously through the first and second wells and the producing the hydrocarbons recovered as backflow occurs simultaneously through the first and second wells.
 15. The method according to claim 10, wherein the first and second wells lack fluid communication with one another across the formation upon initiating the injecting of the conditioning fluid.
 16. The method according to claim 10, wherein the displacement fluid includes steam.
 17. The method according to claim 10, wherein the displacement fluid includes at least one constituent selected from solvent for the hydrocarbons, water, steam, emulsifiers, air, oxygen and carbon dioxide.
 18. The method according to claim 10, wherein the conditioning fluid is injected alone and consists of a solvent for the hydrocarbons.
 19. The method according to claim 10, wherein the conditioning fluid includes a solvent for the hydrocarbons that includes a liquid component under reservoir conditions and a gaseous component under reservoir conditions.
 20. The method according to claim 10, wherein the first and second wells are spaced between 5 meters and 50 meters apart. 